1. Field of the Invention
The present invention relates to a light scanning system and an image forming apparatus employing the same. More particularly, the present invention relates to a light scanning system having a sinusoidally vibrating deflecting surface and an image forming apparatus employing the light scanning system.
2. Description of the Related Art
Light scanning systems, such as laser scanning units (LSUs), are applied to image forming apparatuses for printing an image on paper, such as copiers, printers or facsimiles. Light scanning systems form an electrostatic latent image by scanning light emitted from a light source, such as a semiconductor laser, onto a photosensitive medium of an image forming apparatus using a video signal. An image is produced by transferring the electrostatic latent image formed on the photosensitive medium to a medium, such as a sheet of paper.
Light emitting systems include a light deflector that scans a laser beam emitted from a laser beam source at a constant speed.
Generally, light scanning systems employ as a light deflector a rotating polygonal mirror that horizontally scans an incident laser beam at a constant linear speed by rotating and reflecting the laser beam. An f-θ lens is used as an image-forming lens so that the rotating polygonal mirror can scan light at a constant speed onto a photosensitive medium, for example, onto a surface of a photosensitive drum, of an image forming apparatus.
However, because the rotating polygonal mirror and a motor for rotating the rotating polygonal mirror are required, the light scanning systems are increased in size and are susceptible to vibration and noise.
An attempt has been made to use a sinusoidally vibrating light deflector as a light deflector.
Japanese Patent Laid-open Publication No. hei 9-33843 (published on Feb. 7, 1997) discloses a light scanning system including a sinusoidally vibrating light deflector. The angle of light, which is reflected by the sinusoidally vibrating light deflector, incident on an image-forming lens varies with time according to a trigonometric function.
Accordingly, in this case, an f-arcsin θ lens is used as an image-forming lens.
The light scanning system employing the sinusoidally vibrating light deflector has advantages of low power consumption, a compact light deflector structure, no metal fatigue, and high durability. However, the structure of the f-arcsin θ lens that is used as the image-forming lens is complex, leading to an obstacle to system miniaturization and cost reduction.
Accordingly, a need exists for a light scanning system having an improved sinusoidally vibrating light deflector.